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Results for “OXIDATION REDUCTION”

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PubMed1974

Uptake and reduction of oxidized and reduced ascorbate by human leukocytes.

Incubation of human leukocytes with dehydroascorbate (DHA) results in an increase in their reduced ascorbate (AA) content and hexose monophosphate shunt (HMS) activity, independent of oxygen supply. Incubation with AA induces these changes only in the presence of oxygen. The increase in HMS activity observed as cell AA increases by 1 micromol is the same during incubation with either DHA or AA. We propose that human leukocytes take up ascorbate as DHA (AA after oxidation to DHA) and reduce it promptly to AA, and that HMS stimulation upon incubation with either AA or DHA is a result of DHA reduction.

Aerobiosis↗
PubMed2006

Thin film voltammetry of spinach photosystem II. Proton-gated electron transfer involving the Mn4 cluster.

Thin film voltammetry was used to obtain direct, reversible, electron-transfer peaks between electrodes and the spinach photosystem II (PS II) reaction center in lipid films for the first time. Three well-defined pairs of reduction-oxidation peaks were found using cyclic and square wave voltammetry at 4 degrees C at pH 7.5, reflecting direct, reversible electron transfer involving cofactors of PS II. These peaks were assigned to the oxygen-evolving complex (OEC) tetramanganese cluster (Em = 0.2 V vs NHE), quinones (Em = -0.29 V), and pheophytin (Em = -0.72 V). PS II that was depleted of the OEC did not give the peak at 0.2 V. Observed Em values, especially for the OEC, may be influenced by protein-lipid interactions and electrode double-layer effects. Voltammetry at pH 6 and at pH 7.5 with a time window of >100 ms revealed that the manganese cluster oxidation is gated by slow deprotonation of a reduced form. Additional rapid protonation/deprotonation steps are also involved in the electrochemical reduction-oxidation pathways.

Electron Transport↗
PubMed1975

[Alterations in several cerebral metabolic indices in patients with epilepsy].

The paper pertains to studies of some metabolic indices in the brain of 106 epileptic patients where fits were of a traumatical and inflammatory etiology and with the duration of the disease from 1-10 years. The examination revealed disorders of the reductive-oxidative processes and carbohydrate metabolism in the brain which were not related to the etiology of epilepsy. A disorder of reductive-oxidative processes were more expressed in focal nonconvulsive fits characteristic for temporal epilepsy. The authors point to a certain correlation between changes in biochemical indices and the duration of the disease.

Adolescent↗
PubMedDate not supplied

[The hypotriglyceridemic effects of polyunsaturated fatty acids: pathogenetic hypothesis].

A large number of experimental and clinical studies focused the attention on the role played by omega-3 polyunsaturated fatty acids on the primary prevention of vascular diseases of atherosclerotic origin, especially influencing plasma triglycerides decrease. Aim of the present work was to investigate whether a relationship between triglyceride synthesis and human energy metabolism could exist, in order to explain the hypotriglyceridemic effect of omega-3 fatty acids that could be due to any thermogenic action. Eight male subjects aged 45 years (from 20 to 62) were studied, selected on the basis of high levels of triglycerides (536.7 +/- 204.3 mg/dl), normal or high levels of total serum cholesterol (219.4 +/- 51.2 mg/dl), normal or low HDL-cholesterol (33.6 +/- 6.3 mg/dl) and moderate obesity (BMI 30.3 +/- 1.7). Anthropometric parameters (body weight, height, waist to hip ratio), body composition measurements (fat free mass, fat mass), biochemical parameters were evaluated before and 10-days after PUFAs supplementation (student t paired test) at the compressive dose of 60 mg/kg BW bis in die. At the end of the observation significant decrease of triglycerides was documented (p < 0.005), while total and HDL-cholesterol did not vary significantly, although improved values were noticed. No change in anthropometric, body composition and energy metabolism parameters was demonstrated, except for respiratory quotient and substrates oxidation: a significant increment of respiratory quotient value (p < 0.05) due both to augmented carbohydrates oxidation (p < 0.05) and correspondent lipid oxidation reduction (p < 0.05) and correspondent lipid oxidation reduction (p < 0.05) without any change in the daily total calorie consumption. In conclusion, from a clinical point of view it is possible to hypothesize, even if in a small number of subjects, that PUFAs hypotriglyceridemic effect could derive from a reduced substrate availability, due to the higher carbohydrate oxidation. In other terms, considering the metabolic cascade of triglyceride synthesis, the augmented drug-induced carbohydrate consumption could provoke a reduced availability of products of intermediate metabolism useful to triglycerides hepatic synthesis.

Adult↗
PubMed2002

Science review: Redox and oxygen-sensitive transcription factors in the regulation of oxidant-mediated lung injury: role for nuclear factor-kappaB.

The primary role of pulmonary airways is to conduct air to the alveolar epithelium, where gas exchange can efficiently occur. Injuries to airways resulting from inhalation of airborne pollutants and parenteral exposure to ingested pollutants that cause oxidative stress have the potential to interfere with this process. A progressive rise of oxidative stress due to altered reduction-oxidation (redox) homeostasis appears to be one of the hallmarks of the processes that regulate gene transcription in lung physiology and pathophysiology. Reactive metabolites serve as signaling messengers for the evolution and perpetuation of the inflammatory process that is often associated with cell death and degeneration. Redox-sensitive transcription factors are often associated with the development and progression of many human disease states and inflammatory-related injury, particularly of the lung. The present review elaborates on the role of the redox-sensitive and oxygen-sensitive transcription factor NF-kappaB in mediating lung injury. Changes in the pattern of gene expression through regulatory transcription factors are crucial components of the machinery that determines cellular responses to oxidative and redox perturbations. Additionally, the discussion of the possible therapeutic approaches of antioxidants, thiol-related compounds and phosphodiesterase inhibitors as anti-inflammatory agents will thereby help understand the oxidant/redox-mediated lung injury mechanisms.

Animals↗
PubMed2002

Science review: redox and oxygen-sensitive transcription factors in the regulation of oxidant-mediated lung injury: role for hypoxia-inducible factor-1alpha.

A progressive rise of oxidative stress due to altered reduction-oxidation (redox) homeostasis appears to be one of the hallmarks of the processes that regulate gene transcription in physiology and pathophysiology. Reactive oxygen species and reactive nitrogen species serve as signaling messengers for the evolution and perpetuation of the inflammatory process that is often associated with the condition of oxidative stress, which involves genetic regulation. Changes in the pattern of gene expression through reactive oxygen species/reactive nitrogen species-sensitive regulatory transcription factors are crucial components of the machinery that determines cellular responses to oxidative/redox conditions. The present review describes the basic components of the intracellular oxidative/redox control machinery and its crucial regulation of oxygen-sensitive and redox-sensitive transcription factors within the context of lung injury. Particularly, the review discusses mechanical ventilation and NF-kappaB-mediated lung injury, ischemia-reperfusion and transplantation, compromised host defense and inflammatory stimuli, and hypoxemia and the crucial role of hypoxia-inducible factor in mediating lung injury. Changes in the pattern of gene expression through regulatory transcription factors are therefore crucial components of the machinery that determines cellular responses to oxidative/redox stress.

Animals↗
PubMed2005

The coexistence of the oxidative and reductive systems in roots: the role of plasma membranes.

Different components of the plasma membrane bound and associated redox system, which participate in the energy transfer from the predominantly reducing intercellular environment to the extracellular oxidizing environment, are reviewed. Special attention is given to plant root cells. An analysis of the plasma membrane-associated redox components, such as the cytochromes, quinones, and different types of oxidoreductases (dehydrogenases, oxidases, peroxidases, and superoxide dismutases), is made, as well as their coupling with naturally occurring extracellular substrates, such as oxygen and its reactive forms, phenols, ascorbate, nitrate, ferric ion, and organic acids. The participation of different free radical species in most of the plasma membrane-bound redox reactions is documented.

Cell Membrane↗
PubMed2006

Biotransformation of geldanamycin and 17-allylamino-17-demethoxygeldanamycin by human liver microsomes: reductive versus oxidative metabolism and implications.

Comparative metabolite profiling of geldanamycin and 17-allylamino-17-demethoxygeldanamycin (17AAG) using human liver microsomes in normoxia and hypoxia was conducted to understand their differential metabolic fates. Geldanamycin bearing a 17-methoxy group primarily underwent reductive metabolism, generating the corresponding hydroquinone under both conditions. The formed hydroquinone resists further metabolism and serves as a reservoir. On exposure to oxygen, this hydroquinone slowly reverts to geldanamycin. In the presence of glutathione, geldanamycin was rapidly converted to 19-glutathionyl geldanamycin hydroquinone, suggesting its reactive nature. In contrast, the counterpart (17AAG) preferentially remained as its quinone form, which underwent extensive oxidative metabolism on both the 17-allylamino sidechain and the ansa ring. Only a small amount (<1%) of 19-glutathione conjugate of 17AAG was detected in the incubation of 17AAG with glutathione at 37 degrees C for 60 min. To confirm the differential nature of quinone-hydroquinone conversion between the two compounds, hypoxic incubations with human cytochrome P450 reductase at 37 degrees C and direct injection analysis were performed. Approximately 89% of hydroquinone, 5% of quinone, and 6% of 17-O-demethylgeldanamycin were observed after 1-min incubation of geldanamycin, whereas about 1% of hydroquinone and 99% of quinone were found in the 60-min incubation of 17AAG. The results provide direct evidence for understanding the 17-substituent effects of these benzoquinone ansamycins on their phase I metabolism, reactivity with glutathione, and acute hepatotoxicity.

Antibiotics, Antineoplastic↗
PubMed1983

Comparison of various atmospheric conditions for isolation and subcultivation of Mycoplasma hyorhinis from cell cultures.

The efficiency of aerobic incubation was compared with incubation under various oxygen and carbon dioxide conditions for the isolation and subcultivation of three strains of Mycoplasma hyorhinis from VERO-cell cultures and subcultivation of three laboratory strains. Under anaerobic conditions with a low oxidation-reduction potential (at or below -115 mV) as obtained in jars, with catalysts, containing mixtures of 5%-10% CO2 in H2, very poor or no growth of any of the six M. hyorhinis strains was observed. When traces of oxygen were present (that is, under conditions with higher oxidation-reduction potentials, e.g. when omitting the catalyst in the above gas mixtures or in 5% CO2 + 95% N2) isolation from cell cultures was successful in most tests, but subcultivation of these primary isolates was seldom possible under these semi-anaerobic conditions. However, in most cases these primary isolates could be subcultivated aerobically, although aerobic conditions were unsatisfactory for isolation in about half of the experiments. Isolation of M. hyorhinis was optimal in 5% O2 + 95% N2, under which condition the isolates could also always be subcultivated. Isolation failed occasionally when 5% O2 + 5% CO2 + 90% N2 was used, thus indicating that 5% CO2 was slightly inhibitory. 5% CO2 in air and 10% CO2 either in air, H2 or N2 were also inadequate for isolation from cell cultures. In contrast to the findings with these cell culture-adapted M. hyorhinis strains, the laboratory strains could be subcultivated easily under all conditions tested except those with an oxidation-reduction potential at or below -115 mV; 100% CO2 was inhibitory for all 6 strains. Our findings may partly explain why M. hyorhinis is often considered "non-cultivable" on artificial media once adapted to cell cultures. The findings emphasize the need to employ also a micro-aerophilic condition (5% O2 in 95% N2) in the examination of cell cultures for mycoplasma.

Aerobiosis↗
PubMed2002

Proton coupling to [4Fe-4S](2+/+) and [4Fe-4Se](2+/+) oxidation and reduction in a designed protein.

The coupling of a single proton to [4Fe-4S]2+/+ oxidation/reduction in a de novo designed iron-sulfur protein maquette is presented. The reduced state pKared is 9.3, and the oxidized state pKaox is <6.5. The reduced state pKared shifts to 8.3 upon incorporation of a [4Fe-4Se]2+/+ cluster, implicating the cluster itself or its primary coordination sphere as the proton-coupling site.

Electron Spin Resonance Spectroscopy↗